Java 5 to 7 upgrade for using new programmatic features released

We are using java 5 in our projects. With Java releasing new versions at quite a good pace than we can think of upgrading to, how can we use the new features of Java. We can always upgrade to the
new version of java/jdk but how do I make use of the new programmatic features. Is there a good starting point for us to guide us in refactoring our java 5 code bases. Also does java 7 preach something which was good in java 6 to be not so good or has provided a better way of doing them.
I hope the book "The Well Grounded Java Developer" has something that I am looking for.

I'm pretty sure our book mentions it, but just in case... All 3 major IDEs (Netbeans is the most advanced at this) will recommend and allow you to automatically update some of your code to use new Java 7 features. However, in terms of using Java 6 features, you'll simply have to look at a good upgrade guide (or at least that change list) and see what new features you want to use.

Since Java5 is past its end‑of‑life, you should have changed to Java6 at least, already. Of course, old code which works well should be treated according to the “if it ain’t broke, don’t fix it” principle.